Xmas light string controller

Discussion in 'LEDs and Optoelectronics' started by John12345, Dec 6, 2017.

  1. John12345

    John12345

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    Hi. I want to control 5 Xmas light strings using one of the light string controllers. One controller is not powerful enough to run many of them at once so I would like to amplify the variable signal. One controller puts out a variable voltage from 0 to 110 VDC. Each string has a resistance of 105 ohms. I would need a circuit or transistor or Mosfet that would be capable of 110VDC and an amperage of about 5 amps (for 5 strings). I tried to measure the amperage of each string and read about 0.15 amps so I must be doing something wrong here or my meter is bad. I bought a Mouser mosfet p/n FCPF099N65S3 which I thought would work but I can’t figure out how to put together the circuit. Any help would be appreciated.
     
    John12345, Dec 6, 2017
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  2. John12345

    kellys_eye

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    You might find the controller operates using thyristors and chops the AC waveform rather than producing a DC output.

    Any chance you can show us the insides of the controller?
     
    kellys_eye, Dec 6, 2017
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  3. John12345

    John12345

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    I'm pretty sure it is a dc output since the 120VAC runs thru a rectifier. Pictures are coming.
     
    John12345, Dec 6, 2017
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  4. John12345

    John12345

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    Here are some pictures Control1.JPG Control2.JPG Control3.JPG
     
    John12345, Dec 6, 2017
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  5. John12345

    kellys_eye

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    The rectifiers provide the DC for the COB device (Chip On Board) - that's the black blob on the stand-up PCB.

    IIRC the AC feeds the rectifiers then the unsmoothed (fullwave rectified DC) is fed across the board and to the three thyristors - check the device markings as I'm almost 100% sure they ARE thyristors which are phase switched by the controlling IC.

    You could fit higher powered thyristors quite easily - the diodes should be good for 1A (or 120W) but can also be uprated if required.

    Things is the board is 'live' and so are the wires to the lights! so you need to take particular care no matter what you do.
     
    kellys_eye, Dec 6, 2017
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  6. John12345

    John12345

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    Thanks. I'm looking into it. The thyristors are XL 1225s. You've been a big help.
     
    John12345, Dec 6, 2017
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  7. John12345

    John12345

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    I replaced one XL1225 SCR with a bigger one of the 3 on the board. I used a TN1610H-6T SCR. The light string comes on fine but it does not get brighter and dimmer with the other 2 color strings as it should do. It stays on all the time at the full illumination. Do you know of another SCR that I should use? Maybe I need to use more resistance somewhere in the circuit. I don’t know. Any more help would be appreciated. Thanks.
     
    John12345, Dec 11, 2017
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  8. John12345

    kellys_eye

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    Re-check the pin polarity of the devices fitted.
     
    kellys_eye, Dec 11, 2017
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  9. John12345

    John12345

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    You are right. The pin out spec for my XL1225 thyristor had to be wrong. It showed the light string connected to the gate. I assume that the gate is connected to the "black blob", the anode is connected to the light string, and the cathode to ground. So I rewired the new SCR (TN1610H-6T) the same way. Now I get no lights at all lit on the new SCR string. Any suggestions? Thanks again for all your help. Does the "black blob" not have enough power to turn on the new SCR? Could I leave the old thyristor on the board and have it power the new SCR? I wouldn't know how to wire it up but it sure sounds good.
     
    John12345, Dec 13, 2017
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  10. John12345

    John12345

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    I found out how to amplify the signal and now have it working. Thanks for all of your help.
     
    John12345, Dec 13, 2017
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